System and Method for Retrieving a Well Tool from a Wellbore

ABSTRACT

A technique utilizes a fishing tool and method for retrieving a fish from a downhole location without removal of a downhole completion. The fishing tool comprises a housing and a piston slidably mounted in the housing. Grip legs are engaged with the piston such that movement of the piston in a first direction along the housing moves the grip legs to a disengaged position for receiving the fish. Subsequent movement of the piston in a second direction causes the plurality of grip legs to move to an engaged position with the fish. The grip legs can be moved between the disengaged and engaged positions after the fishing tool is moved through the completion.

BACKGROUND

In a variety of well applications, completions are deployed in wellbores that have wellbore casings along the wellbore wall. Sometimes, downhole tools are lost within the casing but beyond the tubing associated with the completion. The lost well tool can become a restriction and block or limit the flow of production fluid up through the completion. The well tool also can create complications for subsequent downhole operations.

Retrieval of the well tool can be accomplished via a fishing operation in which a fishing tool is deployed downhole from a surface rig. The fishing tool comprises a latching or attachment end designed to engage the well tool, i.e. fish, to be retrieved. However, deploying a fishing tool past the completion can be very complicated. Often, a work-over rig is used to first retrieve the completion and then the fishing operation is conducted to retrieve the fish. This results in an expensive and time-consuming process for retrieving the well tool. As a result, the well tool is sometimes left downhole in spite of the potential for production flow blockage and additional complications during subsequent operations downhole

SUMMARY

In general, the present invention provides a fishing tool and method for retrieving a fish from a downhole location. The design of the fishing tool enables it to be moved downhole through a completion, thereby avoiding the need to remove the completion. The fishing tool comprises a housing and a piston slidably mounted in the housing. A plurality of grip legs are engaged with the piston such that movement of the piston in a first direction along the housing causes the grip legs to move to a disengaged position for receiving the fish. Subsequent movement of the piston in a second direction causes the plurality of grip legs to move to an engaged position with the fish. Actuation of the grip legs can be conducted after the fishing tool is moved through the completion.

BRIEF DESCRIPTION OF THE DRAWINGS

Certain embodiments of the invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and:

FIG. 1 is a front elevation view of a fishing tool system being deployed into a wellbore to retrieve a fish, according to an embodiment of the present invention;

FIG. 2 is a front elevation view of the fishing tool system with a fishing tool actuated to a disengaged position to retrieve the fish, according to an embodiment of the present invention;

FIG. 3 is a front elevation view of the fishing tool system with the fishing tool actuated to an engaged position latched onto the fish, according to an embodiment of the present invention;

FIG. 4 is an orthogonal, cut away view of an embodiment of a fishing tool used with the fishing tool system of FIG. 1, according to an embodiment of the present invention;

FIG. 5 is an orthogonal, cut away view of a housing used in the fishing tool of FIG. 4, according to an embodiment of the present invention;

FIG. 6 is an orthogonal, cut away view of a piston used in the fishing tool of FIG. 4, according to an embodiment of the present invention; and

FIG. 7 is an edge view of a gripping leg used in the fishing tool of FIG. 4, according to an embodiment of the present invention.

DETAILED DESCRIPTION

In the following description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood by those of ordinary skill in the art that the present invention may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.

The present invention relates to a system and methodology for performing a fishing operation. The system and methodology utilize a fishing tool that can be moved past a completion located in a wellbore. The fishing tool is easily adapted for different size wellbores and completions while being amenable for attachment at the end of many types of fishing assemblies.

For example, the fishing tool can be rigged up at the end of a fishing tool assembly deployed downhole on a coiled tubing string. In one embodiment, the coiled tubing string is run in hole with the fishing tool attached while fluid is pumped downhole through the coil tubing string and fishing tool. The pumped fluid prevents accumulation of debris inside the fishing tool. Once the fishing tool is moved past the completion, the pumping rate is increased to actuate the fishing tool to a disengaged position. For example, the fishing tool can be actuated to move grip legs outwardly toward or against the surrounding casing wall until the fish is reached. In this example, the fishing tool is moved slowly into engagement with the fish until a pressure increase is indicated at the surface. At this point, the pumping of fluid down through the fishing tool is stopped to enable the grip legs to retract to an inward, engaged position, as described in greater detail below.

Referring generally to FIG. 1, one example of a well system 20 is illustrated according to an embodiment of the present invention. In this example, well system 20 comprises a fishing tool assembly 22 having a fishing tool 24 that is being delivered downhole into a well via a conveyance 26, such as a coiled tubing conveyance. The fishing tool 24 is moved downhole through a completion 28 and towards a well tool 30, i.e. fish, which is to be retrieved.

The completion 28 is located in a wellbore 32 that is lined with a well casing 34. As illustrated in FIG. 1, wellbore 32 extends down from surface equipment 36 positioned at a surface location 38. Surface equipment 36 may comprise a rig for deploying fishing tool 24 and conveyance 26. Fishing tool 24 is appropriately sized for movement through and past the completion 28 to enable retrieval of the fish 30 from a section of the wellbore 32 below completion 28 without removing completion 28. During movement downhole, a fluid may be pumped down through conveyance 26, e.g. coil tubing, and through fishing tool 24, as indicated by arrows 40. The flow of fluid prevents debris from accumulating in fishing tool 24 during run in of the fishing tool.

In the embodiment illustrated, fishing tool 24 comprises a latching mechanism 42 designed for attachment with fish 30. The latching mechanism 42 may comprise a plurality of grip legs 44 that are mounted for cooperation with a fishing tool housing 46. During deployment of fishing tool 24 through completion 28, the grip legs 44 are held in an inward or engaged position to enable movement of the fishing tool through the confines of completion 28. Once the fishing tool 24 is moved past the distal or lower end of completion 28, fishing tool 24 is actuated to a disengaged position, as illustrated in FIG. 2.

The disengaged position can be adjusted according to the type of fish to be retrieved and the corresponding latching mechanism 42. In the example illustrated, however, the disengaged position is achieved by moving grip legs 44 outwardly toward casing 34. Movement of grip legs 44 to the disengaged position is enabled by increasing the flow of fluid (see arrows 40) down through conveyance 26 and fishing tool 24. As illustrated in FIG. 2, the grip legs 44 may be pivoted outwardly into contact with casing 34 to ensure engagement with fish 30 regardless of the orientation of fish 30 within wellbore 32. The grip legs 44 can be biased to this outward, disengaged position by, for example, springs 48.

Upon actuation of grip legs 44 to the outward position, fishing tool 24 is lowered onto fish 30. The fishing tool 24 is then actuated to the engaged position in which grip legs 44 move inwardly to close over fish 30, as illustrated in FIG. 3. Actuation to the engaged position enables retrieval of fish 30 and can be induced by stopping the downward flow of fluid through conveyance 26 and fishing tool 24.

Referring generally to FIG. 4, one embodiment of fishing tool 24 is illustrated in greater detail. In this embodiment, fishing tool 24 comprises housing 46 and grip legs 44 having connection ends 50 that are selectively moved into and out of housing 46. In FIG. 4, connection ends 50 are illustrated as pulled into housing 46 which forces the grip legs 44 to pivot inwardly to the inward, engaged position. When connection ends 50 are moved out of housing 46, springs 48 cause the grip legs 44 to pivot outwardly to the disengaged position (see FIG. 2).

As illustrated, fishing tool 24 also comprises a piston 52 slidably mounted within housing 46 and connected to grip legs 44. When piston 52 moves relative to housing 46 in one direction, grip leg connection ends 50 are forced out of housing 46 to enable pivoting of grip legs 44 to the outward, disengaged position. Upon movement of piston 52 in another/opposite direction, connection ends 50 are pulled into housing 46 and grip legs 44 are forced inwardly to the inward, engaged position. Piston 52 may be biased in a direction that pulls connection ends 50 into housing 46 by a suitable spring 54 positioned within housing 46.

The fishing tool is operated hydraulically with a flow of liquid that can be placed under increased or decreased pressure as necessary to actuate the fishing tool. The fishing tool is designed to enable liquid flow therethrough to clear debris from the fishing tool during movement downhole. When the liquid flow is increased, however, pressure builds up against piston 52 and moves piston 52 within housing 46 against the bias of spring 54. The piston movement pushes grip legs 44 out of housing 46 so the grip legs can expand toward the casing walls to swallow the fish. As the fishing tool 24 swallows the fish via continued downward movement of conveyance 26, the fish tends to push against piston 52 which restricts flow and provides a pressure increase indication to the surface. At this time, the flow of fluid down through the fishing tool 24 is stopped and spring 54 moves piston 52 in an opposite direction, drawing connection ends 50 back into housing 46. As the connection ends 50 are pulled back into housing 46, the grip legs 44 are pivoted inwardly into a locked position on the fish 30.

Housing 46 may be constructed in various sizes and configurations depending on the specific fishing applications. One example of housing 46 is illustrated in FIG. 5 and comprises a generally cylindrical housing having a connection end 56 for connection to a variety of fishing assemblies. By way of example, connection end 56 may be a threaded connection end for threaded engagement into a fishing assembly. Opposite connection end 56, housing 46 comprises a locking end 58 into which connection ends 50 of grip legs 44 are drawn to lock the grip legs into the engaged position.

As illustrated, the housing 46 comprises an abutment ring 60 against which spring 54 is trapped by piston 52. A passage 62 extends axially through the abutment 60 and has one or more O-rings 64 that seal against a shaft portion 66 of piston 52, as illustrated best in FIG. 6.

As further illustrated in FIG. 6, piston 52 comprises a head portion 68 on one end of shaft portion 66 and a connection region 70 disposed on an opposite end of shaft portion 66. An axial flow passage 72 extends through piston 52 to enable fluid flow therethrough. In some embodiments, the maximum rate of flow that can be moved through flow passage 72 without shifting piston 52 is adjustable via a variable port 74. Variable port 74 can be interchangeable or otherwise variable to increase or decrease the amount of fluid that can be flowed through fishing tool 24 without shifting fishing tool 24 to the disengaged position.

Head portion 68 comprises a pressure surface 76 against which pressure is applied to move piston 52 against spring 54 and thereby actuate fishing tool 24 to the disengaged position. Pressure is applied by increasing the fluid flow downhole beyond the capacity of flow passage 72 such that pressure increases against surface 76 and shifts piston 52 relative to housing 46. Head portion 68 may further comprise an O-ring 78 that is positioned to form a seal with the interior of housing 46.

Connection region 70 may be constructed in a variety of configurations depending on the desired method of attaching grip legs 44. By way of example, connection region 70 may comprise a plurality of pivots designed for connection with corresponding pivots 80 of grip legs 44, as further illustrated in FIG. 7. By way of example, the grip legs 44 may be pivotably mounted to connection region 70 in a manner that captures connection ends 50 between connection region 70 and the surrounding locking end 58 of housing 46 when connection ends 50 are drawn into housing 46. Furthermore, springs 48 can be connected between connection region 70 and grip legs 44; or the springs can simply be positioned to act against grip legs 44 in a manner that pivots the grip legs outwardly when piston 52 axially moves connection ends 50 out of the locking constraints of housing 46.

Grip legs 44 can be formed in a variety of configurations depending on the environment in which they are used and the types of well tools to be retrieved. In the example illustrated, each grip leg 44 comprises an elongate body 82 extending from its connection end 50. The elongate body 82 may comprise a plurality of teeth 84 that function to securely grip and hold the fish 30. By way of example, the teeth 84 may be oriented in an upward direction toward housing 46 to further facilitate the gripping and holding of fish 30.

In operation, the design of fishing tool 24 enables movement of the fishing tool past completions located in wellbore 32. Application of sufficient fluid flow downhole to the fishing tool 24 increases pressure against pressure surface 76 of piston 52 so that piston 52 is shifted against the bias of spring 54. Upon sufficient movement of piston 52 relative to housing 46, grip legs 44 become free of locking end 58 of housing 46 and transition to a disengaged position. Conveyance 26 is then used to move grip legs 44 over the fish 30, and the pressure against piston 52 is released. This allows spring 54 to shift piston 52 in an opposite direction along housing 46, thereby drawing connection ends 50 of grip legs 44 back into housing 46. Movement of connection ends 50 into housing 46 forces grip legs 44 to pivot inwardly and lock onto fish 30 for retrieval from the wellbore. The fish 30 can be released simply by pumping fluid at a sufficient rate to again create adequate pressure against piston 52 to shift the piston relative to housing 46 and move grip legs 44 to the disengaged position.

The present system and methodology can be used to enable fishing operations in a variety of well configurations. The system and methodology further enable fishing operations to be conducted in a more time efficient and cost efficient manner by avoiding the need for removal of completions. Additionally, fishing tool 24 can be utilized with a variety of fishing tool assemblies, and the size and component configuration can be adjusted based on factors related to the fish to be retrieved, the wellbore environment, the completion equipment, and the other equipment utilized in the fishing operation.

Accordingly, although only a few embodiments of the present invention have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this invention. Such modifications are intended to be included within the scope of this invention as defined in the claims. 

1. A device for use in a well, comprising: a fishing tool to engage a fish in a wellbore, the fishing tool comprising: a housing; a piston slidably mounted in the housing; a plurality of grip legs engaged with the piston, wherein movement of the piston in a first direction along the housing causes the plurality of grip legs to move to a disengaged position for receiving the fish and movement of the piston in a second direction causes the plurality of grip legs to move to an engaged position.
 2. The device as recited in claim 1, wherein the piston is spring biased to move the plurality of grip legs to the engaged position.
 3. The device as recited in claim 2, wherein the piston comprises a fluid flow passage through which fluids can be flowed axially through the piston.
 4. The device as recited in claim 3, wherein the piston comprises a variable size port positioned in the fluid flow passage to allow a desired flow rate through the piston.
 5. The device as recited in claim 1, wherein each grip leg of the plurality of grip legs comprises a connection end pivotably connected to the piston.
 6. The device as recited in claim 5, wherein each grip leg is spring biased to pivot the grip leg toward the disengaged position.
 7. The device as recited in claim 6, wherein movement of the connection end of each grip leg into the housing forces the grip leg toward the engaged position.
 8. The device as recited in claim 1, wherein each grip leg of the plurality of grip legs comprises a plurality of teeth oriented to hold the fish when the plurality of grip legs are in the engaged position.
 9. A method of forming a fishing tool, comprising: slidably mounting a piston within a housing sized to move through a completion within a wellbore; providing the piston with a pressure end against which fluid pressure is applied to move the piston within the housing; pivotably connecting a plurality of grip legs to the piston in a manner that allows the grip legs to pivot between an outward position and an inward position as the piston is moved through the housing.
 10. The method as recited in claim 9, further comprising biasing the plurality of grip legs toward the outward position.
 11. The method as recited in claim 10, wherein biasing comprises spring biasing.
 12. The method as recited in claim 9, further comprising biasing the piston in a direction that would move the grip legs to the inward position.
 13. The method as recited in claim 12, wherein biasing comprises spring biasing.
 14. The method as recited in claim 9, further comprising forming an axial flow passage through the piston to enable a desired amount of fluid flow through the fishing tool.
 15. The method as recited in claim 9, further comprising using the housing to force the plurality of grip legs to the inward position when the piston is moved in the appropriate direction.
 16. A method of fishing for a tool in a wellbore, comprising: moving a fishing tool downhole through a completion in the wellbore; applying sufficient pressure against a piston of the fishing tool to cause a plurality of grip legs to move to a disengaged position; placing the plurality of grip legs in a position to engage a fish within the wellbore; and causing the piston to move in an opposite direction and pivot the plurality of grip legs into engagement with the fish to allow retrieval of the fish through the completion.
 17. The method as recited in claim 16, wherein moving comprises moving the fishing tool downhole on coiled tubing.
 18. The method as recited in claim 16, further comprising pumping fluid through the fishing tool to clear debris from inside the fishing tool.
 19. The method as recited in claim 16, wherein applying sufficient pressure comprises pivoting the plurality of grip legs outwardly until the plurality of grip legs contacts a surrounding casing.
 20. The method as recited in claim 16, further comprising spring biasing the plurality of grip legs toward the disengaged position.
 21. The method as recited in claim 16, wherein causing comprises gripping the fish with a plurality of teeth disposed on each grip leg of the plurality of grip legs.
 22. A system for fishing in a wellbore, comprising: a coiled tubing string; and a fishing tool assembly mounted to the coiled tubing string, the fishing tool assembly comprising a fishing tool having: a housing; a piston slidable within the housing; and a plurality of movable grip legs that cooperate with the piston such that movement of the piston enables movement of the plurality of movable grip legs between engaged and disengaged positions.
 23. The system as recited in claim 22, wherein the plurality of movable grip legs are pivotably mounted to the piston.
 24. The system as recited in claim 23, wherein the housing is positioned to force the plurality of movable grip legs to the engaged position upon movement of the piston in a first direction.
 25. The system as recited in claim 24, wherein the plurality of movable grip legs are biased toward the disengaged position, such that movement of the piston in a second direction enables movement of the plurality of movable grip legs to the disengaged position. 